Process relating to the production of synthetic lumber from cornstalks



Patented May 5, 1931 UNITED STATES PA'TENT; OFFICE; f

ORLAND R. SWEENEY, E AMES, IOWA, ASSIGNOR TO IOWA STATE OF AGRICULTURAL AND MECHANICAL ARTS, OF AMES, IOWA, A CORPORATION OI IOWA PROCESS RELATING TO THE PRODUCTION OF SYNTHETIC LUMBER FROM .CORNSTAIIKS No Drawing.

This invention relates to the processes involved in manufacturing and producing synthetic lumber from corn-stalks by means of, first, cooking the unshredded corn plant under pressure; second, allowing it to stand for a certain length of time without washing it; third, passing it through a rod mill; fourth, suitably washing the same; fifth, passing the washed product through a refining machine;

sixth, chemically treating the same, and

seventh, forming it into board and drying it on a suitable machine, and has for its object to provide a material similar to lumber that is economical in manufacture, durable and strong in use and refined in appearance. The

. step by step procedure as above may be varied as will hereinafter be explained.

Heretofore, a great deal of experimenting has been done in attempting to make this class of material from cornstalks, and much difficulty has been experienced, especially in commercial plants. Examination of the cornstalk shows that it is composed of a hard outer shell called the cortex. This cortex surrounds a soft pulpy material known as pith or parenchyma, and this pith surrounds elon ated cell fibers called vascular bundles: ny processing of this material is diificult because of the different physical properties.

.to shred or otherwise comminute the cornstalks before subjectin them to cooking or chemical treatment. have found that if the corn-stalks be unshredded and then fed into the digester as they come in bales or directly from the field, before they have been Application filed June 27,

1929. Serial No. 374,2?4.

given any serious mutilation, and that'if the digestion be carried out using approximately pure water, or in other words water whose pH value does not vary greatly from 7.0, and that if these whole unmutilated stalks are subjected to a pressure of about thirty pounds in contactwith hot water, that there results a product which when properly macerated gives a board of great strength and of highly desirableproperties for use in the arts.

I have also found that it is advisable aftercooking the cornstalks for approximately three hours under a pressure of thirty pounds with hot water, that the fibers will be made tougher and that the pitch cells will draw into fiber better and be removed more completely from the fibrous cortex cells if I allow the cooked stalks to stand for from four to twenty-four hours before they are further handled in the processes.

This standing has a double advantage in that it allows the fibers to absorb from the cook liquors ligneous or pentosic materials which probably partly oxidize and at the same time the greater amount of the cooking liquors drain away thus reducing the necessity for excessive washing of the material.

In order to get the best results from the water digested fibers or cornstalks as prepared in the foregoin manner, I next pass the cornstalks throug a heavy rod mill. This rod mill is of the usual construction consisting of a large drum mounted for ro tation and having a plurality of heavy rods therein. As the drum revolves on its axis the rods naturally either tumble over each other or rise upon the side of the drum and slide down continuously. It is obvious that if the rods tumble from the top portion of the drum downwardly, a pounding action will result, whereas if the rods slide down the side they will give a rubbing action to the material inside the drum. For our purposes we prefer the rubbing action as it draws the pith cells into long fibers which do not jell up and which work better when commingled with the tough, strong cortex fibers. The obtaining of this result will vary with the different types of rod mills, but any skilled workman can easily determine the speed the drum should rotate for realizing this rubbing action. Results will also depend on the rate the cornstalks are fed into the mill. Obviously the larger the rods and rod mill the greater the feed must be in order to pro duce satisfactory fiber. -I have found that it is best to run the cornstalks through at such a rate as to cause the cortex fibers at the dischar e end to vary in lengths from very short fibers to fibers of about one-half inch in length. Best results are not obtained by attempting to completely reduce the pulp in the rod mill.

By passing the cornstalks through at a rate to give fibers of the above mentioned dimensions, the pith is not excessively jelled. There will also be produced a small percentage of thread-like fibers several inches in length which is very desirable.

It is necessary to feed into the rod mill at the same time that the stalks are going through, an amount of water such as to make the cornstalk fiber come from the discharge freely. The amount of this water will be at least five hundred per cent of the weight of the corn-stalks fed into the mill.

After the pulp has come through the mill it is now coarse enough to be free on a screen which is so positioned as to receive the pulp. It is upon this screen that the cornstalk pulp is Washed with water to remove a certain amount of the pentosans and lignins produced during the water cooking. This washing must not be too thorough because the adhesive properties of these before-mentioned materials are desirable. If, however, none of the lignins or pentosans are washed out, the board will not be free enough on the machines used to make up the same. The screen should be of approximately forty mesh and may be either of the inclined sheet type or the rotating cylinder type. As the pulp travels down and across the screen it is aided by the water sprayed on it which can be controlled by a valve in the water line.

After washing the pulp it can be made directlyinto lumber but it will contain pieces of cornstalk pulp which are rather large, giv ing an unsightly board. Where this is not objectionable a board may be manufactured very cheaply. To produce a more refined board the pulp from the washing screen is next passed through a refiner in order to take out the small pieces of material which are sometimes termed shiners or chives.

For removing the shiners or long pieces of cornstalks I have found that the Jordan machine commonly used by the paper mills with knives set widely apart is quite satisfactory. Another machine that is very satisfactory is the Claflin machine which is well known also to all paper mill manufacturers and even a buhrstone mill will do most excellent work.

In passing the pulp through the refiner it is necessary to add an additional quantity of water, in order that the same will pass freely through it. The pulp emerging from the refiner machine should be free enough to work on the board forming machine that is being used. If the packing between the knives of the Jordan or Olaflin mills be removed the heavy particles by centrifugal force are carried out between the knives and are disintegrated in the mill. The finer fibers are not cut finer and the product thus produced is satisfactory for working on almostany of the types of board forming machines now available.

Either before or after the material has passed through the final refining it can be subjected to any process of water proofing or sizing that is now commonly used. In particular I have found that this material when treated-With rosin and alum Works unusually well on a type of machine which I have developed and which is the subject of another patent. In sizing I have found that the best results are obtained by adjusting the pH value of the solution to approximately 4.5.

In the operation of the process a pulp of from three to one per cent consistency can be worked. About one and one-half to two per cent pu p suspension works well. On the board forming machine the water is largely removed from the pulp; the pulp forming a wet mat which is pressed and dried.

The water thus removed is generally called white waters and I have found that for economy of water consumption it is desirable to use this water by returning it to the process. I use it direct for washing the pulp and for diluting the pulp in the refining machine. If used to cook the stalks it is necessary to adjust the pH value to approximately 7.0.

It is well known that corrosive sublimate is very poisonous to termites or ants which are frequentl troublesome in attacking cornstalk and 0t er insulating lumber. have found that if I add to the pulp suspension a few hundredths of a per cent of corrosive sublimate that it is absorbed by the fibers and effectively protects the board against such insects. Also under certain conditions and articularly in damp places certain molds are armful to insulatlng lumber. I have found that it is possible to incorporate a small amount of copper sulfate into the pulp mass. This copper sulfate, or other soluble copper salt, is precipitated out by the addition of lime or generally will be absorbed when the water proofing material is added,

'ving sufficient copper concentration to efectively protect the lumber. In the process where the white waters are used over again it is feasible to continuously feed in the copper sulfate or corrosive sublimate, and since the white waters is returned to the process there will be no loss of these materials except as they are absorbed in the board.

In the process of making this class of lumber it is common practice to over dry the lumber in the dryers used, and then to bring the moisture content up to approximately ten per cent of the weight of the lumber by spraying the proper amount of water on the surface of the board.

I have found that I can dissolve copper sulfate and corrosive sublimate, either or by milling, and-last forming 1t into lumber by a suitable machine.

2. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the cooking of the unshredded, corn plant in water under pressure, discharging the material from the cooker, breaking the material intoparticles by millin and last forming it into lumber by a suitable machine.

3. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the cooking of the unshredded corn plant in hot waterunder pressure, removing the same from the hot water, disintegrating the material by milling, and then forming it into lumber by asuitable drying and pressing machine.

4. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the cooking of the shredded corn plant at a pressure of approximately thirty pounds in water, subjecting the cooked material to a mill, andthen forming it into lumber by a suitable drying and pressing machine.

5. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the cooking of the unshredded corn plant at a pressure of approximately thirty pounds in water of pH value of approximately 7.0 for several hours, subjecting the cooked material to a mill, and then forming it into lumber by a suitable drying and pressing machine.

6. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the cooking of the unshredded corn plant in water of approximately 7.0 pH value, rubbin and breaking the cornstalks into elongate particles by a rod mill, and

7. The process of manufacturing and producing synthetic lumber from cornstalks consisting in the soaking of the unshredded corn plant in liquid, subjecting the soaked material to milling, and then forming it into suitable shape by forming and drying it with suitable means.

8. The process of manufacturing and producing synthetic lumber from cornstalks consisting in cooking the entire unshredded corn plant at a pressure of approximately thirty pounds in water of pH value of approximately 7 .0 for a period offrom three to five hours, discharging the material from the cooking process and allowing it to stand without washing for a period of several hours, milling the cooked seasoned corn plant but-not completely pulping it, washing the material so that a part but not all of the gums developed in the cooking be removed, passing the washed material through a refining machine, and drying and pressing the material into lumber.

9. The process of manufacturing and producing synthetic lumber from cornstalks consisting in cooking the entire mass in hot water, removing the surplus water and allowing the cornstalks to stand several hours, the rubbing and breaking of the cornstalks into elongated particles, washing the particles to remove a part'of the gums developed in the cooking, and then pressing and drying the same into lumber.

10. The process of manufacturing and pro- *ducing synthetic lumber from cornstalks consisting in cooking the entire mass in water, removing the cornstalks from the water, breaking the cornstalks into elongated particles by subjecting the cornstalks to a rod mill, washing the material from the rod mill, pressing the white waters out of the material and drying the same into lumber, and return- 4 ing the white waters for washing and diluting additional cornstalk material coming through the processes.

ORLAND R. SWEENEY.

then forming it into suitable shape by a forming and drying machine. 

